Heart valve

ABSTRACT

Improved versions of heart valve prostheses include the usual generally annular body having an interior surface defining a blood flow passageway and having one or two occluders supported thereon for alternately blocking and then allowing the flow of blood in a predetermined direction. Notches are formed at opposite locations in the periphery of an occluder, and each is disposed about a pivot post that projects radially inward from the interior surface of the annular body. A pair of stops flank each pivot post, having curved surfaces at locations adjacent to the pivot posts but radially inward from the ends thereof that function as oppositely disposed fulcrums and cooperate with the pivot posts in defining the opening and closing movement of each occluder. Preferably, the pivot posts and the stop means are formed as an integral structure. Self-centering seats can be used to provide a better seal in the closed position.

This application is a continuation-in-part of my earlier applicationSer. No. 653,960, filed Sept. 24, 1984, abandoned 9/17/86.

This invention relates to heart valve prostheses for replacement ofdefective natural valves and more particularly to heart valve prostheseswhich employ one or more occluders in the form of flat platelikemembers, although certain features of the invention are applicable tovalves having curved occluders.

BACKGROUND OF THE INVENTION

Various types of heart valve prostheses have been developed whichoperate hemodynamically as a result of the pumping action of the heartand which are in essence functioning as check valves. Early heart valvesemployed a ball-and-cage arrangement whereas later versions of heartprostheses have employed one or more occluders generally in the form ofa plate or disc which might be flat or of a curved shape. Bokros U.S.Pat. No. 3,546,711 shows a heart valve having a circular occluder whichis pivoted from a hinge pin that coacts with a pair of upstanding finslocated on the downstream surface of the occluder. Bokros U.S. Pat. No.4,178,639 shows a bi-leaflet heart valve having a pair of platelikemembers each of which has ears extending from its opposite lateral edgesthat pivot in spheroidal guides located in the orifice ring. U.S. Pat.No. 3,445,863 shows a heart valve arrangement having one or moreoccluders in the form of flat plates having cut-outs at their edgeswhich are proportioned to interfit with complementary cut-outs in a basering formed of generally similar material. U.S. Pat. No. 4,225,980 showsa metallic heart valve which includes an oval-shaped occluder havingcut-outs in opposite lateral edges which coact with parabolic pivots orpegs that extend radially inward from the interior surface of theorifice ring. U.S. Pat. No. 4,078,268 shows a bi-leaflet valve having apair of semicircular occluders which have ears extending upward from thedownstream surface thereof that co-act with fulcrums to effect apivoting action. U.S. Pat. No. 4,159,543 shows a variety of bi-leafletvalves, one version of which has grooves cut into the edges of thesemicircular occluders at an oblique angle to the surface thereof, whichgrooves receive generally conical pivot pins that extend radially inwardfrom the interior surface of the orifice ring. U.S. Pat. No. 4,373,216illustrates heart valves having one or more occluders that have notchesin opposite edges of the periphery thereof which co-act with elongatedprotuberances extending inward from the surface of the orifice ring andproviding tracks for guiding pivotal and translational movement of theoccluders.

As is apparent from the foregoing, a wide variety of different heartvalves have been designed, and work continues on new heart valve designsin order to still farther improve the functioning of these prostheseswhich are being used in greater quantity each year as surgicaltechniques improve throughout the world.

SUMMARY OF THE INVENTION

The invention provides improved versions of heart valve prostheses whicheach include the usual generally annular body having an interior surfacedefining the central blood flow passageway along with one or moreoccluders supported thereon for alternately blocking and allowing theflow of blood in a predetermined direction, in generally check-valvefashion. Formed at opposite locations in the periphery of an occluder isnotch means which may be generally rectangular in shape, each of whichreceives a pivot post that projects radially inward from the interiorsurface of the annular body. In flanking locations to each pivot postare a pair of stop means that present curved surfaces in the regionsadjacent to the pivot posts at locations radially inward from the endsof the pivot posts. These curved surfaces function as oppositelydisposed fulcrums that cooperate with the pivot posts in defining theopening and closing movement of the occluder. Preferably, the pivotposts and the stop means are formed as an integral structure so as toavoid any gap therebetween which would provide a stagnant region whereblood clotting might occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a bi-leaflet heart valve embodyingvarious features of the invention, shown in the open position.

FIG. 2 is an enlarged sectional view taken generally along the line 2--2of FIG. 1.

FIG. 3 is a fragmentary view similar to FIG. 2 showing the leaflets inthe closed position.

FIG. 4 is a fragmentary view, similar to FIGS. 2 and 3, of the orificering with the leaflets being shown in broken lines in an approximateposition they might assume during opening movement.

FIG. 5 is a fragmentary plan of the orifice ring shown in FIG. 4.

FIG. 6 is a fragmentary sectional view taken along line 6--6 of FIG. 5.

FIG. 7 is a side view of one of the occluder leaflets with portionsbroken away to illustrate its interior structure.

FIG. 8 is a fragmentary sectional view taken generally along the line8--8 of FIG. 2.

FIG. 9 is a perspective view of an alternative embodiment of an annularbody suitable for use as a part of a single-occluder heart valve.

FIG. 10 is a fragmentary plan view of the annular body shown in FIG. 9.

FIG. 11 is a perspective view of the heart valve showing the annularbody of FIG. 9 with the occluder installed and in the open position.

FIG. 12 is a side view of the occluder with a portion broken away toshow its internal construction.

FIG. 13 is a fragmentary front view of the occluder.

FIG. 14 is a sectional view of the heart valve shown in FIG. 11depicting in full lines the occluder in an intermediate position as itis moving to the closed position and with the occluder shown twice inbroken line in the position which it assumes in the open position and inthe closed position.

FIG. 15 is an enlarged fragmentary view of the interior surface of theannular ring emphasizing the pivot support area.

FIG. 16 is a plan view of an alternative design bi-leaflet heart valveembodying various features of the invention, shown in the closedposition.

FIG. 17 is an enlarged sectional view taken generally along the line17--17 of FIG. 16.

FIG. 18 is an enlarged fragmentary plan view of the orifice ring shownin FIG. 16.

FIG. 19 is a fragmentary view of a leaflet.

FIG. 20 is a side view of an occluder leaflet.

FIG. 21 is a fragmentary view, similar to FIG. 17, of the orifice ringwith the leaflets removed greatly enlarged in size.

FIG. 22 is a fragmentary sectional view taken along line 22--22 of FIG.21.

FIG. 23 is a fragmentary sectional view taken generally along the line23--23 of FIG. 21.

FIG. 24 is a perspective view of another alternative embodiment of abi-leaflet heart valve.

FIG. 25 is a side view of the heart valve of FIG. 24 with the occludersin the open position.

FIG. 26 is a side view of the heart valve with the occluders in theclosed position.

FIG. 27 is a fragmentary plan view of the annular body shown in FIG. 24enlarged in size and with the leaflets removed.

FIG. 28 is a fragmentary view, similar to FIG. 17, of the orifice ringand one leaflet greatly enlarged in size.

FIG. 29 is a fragmentary plan view of one of the leaflets.

FIG. 30 is a side view of an occluder leaflet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated in FIG. 1 is a heart valve 21 which consists of an annularvalve body or housing 23 which supports a pair of pivoting lealets oroccluders 25 that open and close to control the blood flow through acentral passageway or orifice which is defined by the interior surface27 of the valve body. Inasmuch as the annular body 23 defines thecentral passageway or orifice, it is sometimes referred to as anorifice-ring. The normal flow of blood through the heart valve 21 isdownward in the orientation in which the valve is shown in FIGS. 1 and2, as represented by the small arrows which appear at the top of FIG. 2.It should, of course, be understood that the valve 21 can operate in anyorientation and is not significantly affected by gravity. Thus, theterms such as upward and downward, as used hereinafter, are merelyemployed to facilitate explanation and understanding and are not meantto place any limitations upon the operation of the heart valves beingdescribed.

As depicted, the annular body 23 has a smooth exterior surface 29 whichis that of the lateral surface of a right circular cylinder. It shouldbe understood that suitable means, such as a peripheral groove or a pairof flats, would usually be provided for attaching a suturing ring to theannular body to facilitate sewing or suturing of the heart valve 21 tothe heart tissue. However, inasmuch as the suturing ring and its meansof attachment to the heart valve 21 form no part of the presentinvention, it is simply omitted so as to facilitate the illustration ofthe specific components of the heart valve with which the invention isconcerned. U.S. Pat. No. 4,233,690, issued Nov. 18, 1980, illustratesone method of attaching a suturing ring to an annular heart valve body,and the disclosure of this patent is incorporated herein by reference.

The valve body 23 and the leaflets 25 may be made of any suitablematerial that is biocompatible and nonthrombogenic and that will takethe wear to which it will be subjected during countless opening andclosing movements of the leaflets. Preferably, the leaflets are made ofisotropic graphite, such as that sold under the tradename POCO and thatpreferably contains between about 5 and about 20 weight percent tungstento render it radio-opaque and allow x-ray visualization, which graphitehas been suitably coated with pyrolytic carbon, such as that sold underthe trademark PYROLITE. The lower portion of FIG. 7 shows the pyrocarboncoating on the graphite substrate. Such pyrocarbon gives excellent bloodand tissue compatibility and wear-resistance.

The orifice ring 23 can be made in the same fashion using apyrocarbon-coated substrate, or it can be, and preferably is, made fromsolid PYROLITE pyrocarbon. A preferred process for forming an orificering from all pyrocarbon by coating a mandrel, which is subsequentlyremoved, is disclosed in European Patent Application, Publication No.0055406 Al, the disclosure of which is incorporated herein by reference.

The illustrated leaflets 25 are flat and have a uniform thicknessthroughout. Each leaflet 25 has a straight-edge portion 31, which isbest seen in FIG. 7 and which is oriented at an angle to the downstreamsurface 33 of the leaflet so that the two straight-edge portions 31 abutin substantially face-to-face contact when the pair of leaflets are inthe closed position as depicted in FIG. 3. Generally, the angle will bebetween about 110° and about 130°, being of course dependent upon theorientation of the leaflets to the horizontal or transverse plane in theclosed position, as depicted in FIG. 3. In addition, each of theleaflets 25 has a major arcuate, nearly semicircular, edge 35 (seeFIG. 1) and a pair of intermediate or transitional straight edgeportions 37 which are flat and perpendicular to the upstream anddownstream surfaces of the leaflets. In addition, each leaflet 25contains a pair of notches 39 disposed in its opposite lateral edges inthe regions of the straight edge surfaces 37. As best seen in FIG. 8,the notches are generally rectangular in shape, and all of the definingedges are rounded as opposed to being sharp.

The passageway-defining interior surface 27 of the annular body 23 alsohas a right circular cylindrical shape for a major portion of its lengthbut is interrupted by a pair of diametrically opposed flat sections 41from which the support means for holding and defining the movement ofthe leaflets 25 radially project. The support means includes a pair ofpivot posts 43, which are sized to fit within the notches 39 and whichpivot posts are flanked by stop means 45, 47. As can be seen from FIGS.1 and 5, the flanking stop means 45, 47 project radially farther inwardthan do the pivot posts 43. Preferably, the pivot posts 43 and theflanking stop means are formed integrally with one another, and mostpreferably this overall support structure is formed as an integral partof the annular body 23, as by machining a pre-shaped body of pyrolyticcarbon to final dimensions. As best seen in FIG. 4, the pivot posts 43each have a pair of opposite arcuate surfaces, a generally upper surface49a and a generally lower surface 49b, which are referred to as thelateral surfaces of the posts 43, so as to be distinguished from theflat end surface 51 of each pivot post.

The leaflets 25 are suitably assembled with the annular ring 23 bysuitably distorting the ring, as by squeezing the ring inward at itsrelatively thin, hollow, cylindrical regions so that the diametricallyopposite, thicker regions where the flat surfaces 41 are located moveaway from each other sufficiently far to allow the insertion of thenotched leaflets. Instead of squeezing, the thicker portions may bepulled outward. An all PYROLITE pyrocarbon annular body 23 hassufficient resiliency to permit this distention and to return to itsoriginally machined configuration. In the assembled heart valve, thedepth of the notch 39 is slightly greater than the length of the pivotpost 43 so that one of the lateral edge surfaces 37 of the leaflet willbear against a facing flat section 41 of the annular body, asillustrated in FIG. 8.

In the open position depicted in FIG. 2, the leaflets 25 lie at an angleof about 5° to 15° to the centerline of the valve passageway with theupper edge surface of the notch 39 in contact with the arcuate surface49a of the pivot post 43, see also FIG. 8. The orientation of theleaflet is maintained and defined generally by contact of the downstreamsurface 33 of the leaflet against side surfaces 53 formed on the centralstop 45. In addition, there will be line contact between the upstreamsurface 32 of the leaflets 25 and an arcuate surface 55 which is formedon the stops 47 in a location that is intermediate of the upstreamsurface 49a and the downstream surface 49b of the pivot post 43 and isspaced radially inward thereof.

When the downstream (downward as depicted in FIG. 2) flow of blood isdiscontinued as the contraction of the respective ventricle terminateswith respect to an aortic valve, the respective ventricle will thenbegin to relax in order to draw more blood into the chamber from theatrium, and as a result the back pressure which is present within theaorta causes blood to tend to flow upstream (upward, as illustrated inFIGS. 2 and 3) causing the leaflets 25 to swing or pivot toward theclosed position. The leaflets are quickly displaced slightly upward sothat the lower surfaces of the rectangular notches 39 bear against thearcuated surfaces 49b of the pivot posts, and the swinging of theleaflets is guided by contact at these points, together with contactbetween the upstream surface 32 of the leaflets 25 and the arcuatesurface 55 on the stops 47.

When the closed position is reached as depicted in FIG. 3, the arcuateedges 35 of the leaflets 25 lie in contact with the interior surface 27of the annular body. Accordingly, the shape of the arcuate edge 35 willgenerally be that of a section of an ellipse, i.e., the intersectionbetween a plane and a right circular cylinder, and the edge ispreferably bevelled as shown (FIG. 7) so as to more closely seat againstthe interior cylindrical surface. In addition, there may be line contactbetween the arcuate surface 55 of the stops 47 and the upstream surface32 of the leaflets, and the straight-edge portions 31 of the twoleaflets 25 will also abut in substantially face-to-face contact, all asshown in FIG. 3. There possibly may also be some slight touching betweenthe downstream surface 33 of the leaflets 25 and region of a pair ofcurved surfaces 57 which are formed on the central stop 45 at locationsjust above the side surfaces 53 and which thus lie intermediate of theupstream and downstream arcuate surfaces 49a,b and radially inward ofthe pivot posts.

When the pumping stroke again occurs, the pressure against the upstreamsurface of the leaflets 25 immediately displaces the leaflets downwardagainst the central stop 45, and pivoting begins guided by the linecontact between the undersurface 33 of the leaflets 25 and the curvedsurfaces 57, as depicted in ghost outline in FIG. 4. In addition, theleaflets will be displaced slightly so that there is contact between theupper surfaces of the notches 39 and the arcuate surfaces 49a on thepivot posts.

By forming the posts 43 and stop means 45, 47 integral with one another,the regions of joinder can be blended together arcuately so there are nosharp depressions or valleys, i.e. no regions of concave curvaturehaving a radius of curvature less than about 0.2 mm., which would belocations ripe for the beginning of clotting; thus, there is asubstantial advantage gained from being able to have such a smoothtransition from surface-to-surface, particularly where the very ends ofthe arcuate surfaces are not necessary for guidance. Moreover, thedesired smooth swinging of the leaflets between the open and closedpositions is farther facilitated by the radius of curvature whichappears on the surfaces 49a and 49b of the pivot posts 43. In thisrespect, the focal point of the radius of curvature of each of thesesurfaces 49a, 49b should lie beyond the center point of the pivot postand may even lie past the opposite side of the pivot post. By examiningthe leaflets in the closed position as shown in FIG. 3, it will be seenthat this arrangement between the arcuate surface 49 a and thesubstantially flat surfaces defining the upper end of the notch 39creates an immediate sharp pivoting movement which tends to more quicklyopen the valve in response to the beginning of the pumping stroke. Inaddition to blending the transition areas between adjacent surfaces,streamlining is also provided as by creating an oblique undersurface 59on the central stop 45.

In summary, the integral pivot post and stop arrangement minimizesinterference with blood flow, while at the same time providing foreffective washing of the surfaces to avoid clotting; moreover, veryeffective and positive control of the swinging of the leaflets isprovided as a result of the short pivot posts 43 which are flanked bythe stop means which protrude farther radially inward into thepassageway and thereby serve not only as stop surfaces, but alsofulcrums to assist the pivoting movement. As best seen perhaps byexamining FIGS. 4 and 8 together, the movement of the leaflet about thesurface 49a as a fulcrum is primarily a rolling action, with a minimumof sliding movement, which is important to reduce wear in a device suchas this that must continue to operate satisfactorily for anindeterminate number of years. The ability to blend the pivot posts intothe stop means, which results from the integral nature of them, allowsthe design to take advantage of the contact between the pivot post andthe stop means which provides overall strengthening of the structurewithout having to suffer the disadvantage of precisely matchingindividually machined components to try to avoid minor crevices andvalleys that might likely promote the formation of blood clotting.

Depicted in FIGS. 9-15 of the drawings is an alternative embodiment of aheart valve 121 which includes an annular body 123 designed to operatewith a singular flat occluder or disc 125. Generally, the sameprinciples of design are executed in the heart valve 121 as werehereinbefore explained in detail with respect to the bi-leaflet valve21, and therefore similar numbers in the 100 series are utilized torefer to comparable components. Moreover, it should be understood that,unless specifically stated hereinafter, the function and construction ofthe comparable components will be essentially the same as previouslydescribed.

The annular body 123 has an interior surface 127 which defines thepassage or orifice through which the bloodstream will flow and isillustrated with a smooth exterior cylindrical surface 129 for thereason set forth hereinbefore. The interior surface 127 does differ fromthat of the bi-leaflet version in that, as described in detailhereinafter, inwardly extending lands 161, 163 are provided againstwhich the arcuate edges of the disc occluder 125 can positively seat.

The occluder 125 generally has the form of a flat disc having anupstream surface 132 and a downstream surface 133. The periphery of thedisc includes a minor arcuate section 131, a major arcuate section 135and a pair of oppositely disposed, straight, parallel intermediatesections 137. Notches 139 of generally rectangular shape are located inthe regions of the straight edge portions 137. The shape of the majorarcuate edge 135 is generally that of a section of an ellipse, and theshape of the minor arcuate edge section 131 is also generally that of asection of an ellipse with a slightly shorter minor axis. As best seenperhaps in FIG. 13, the intermediate edge portions are each inwardlyoffset from the outermost lateral extension of the major edge surface byshort perpendicular transitional surfaces 138 that are collinear. Asbest seen in FIG. 12, the circular disc is also preferably made ofisotropic graphite which has been coated with PYROLITE pyrolitic carbon.

The pivot and stop means arrangement is also preferably formedintegrally as a part of the annular body 123 for the reasons ashereinbefore described with regard to the annular body 23 illustrated inFIGS. 1 through 8; however, the design of the arrangement differssomewhat because of the single occluder concept. Instead of forming apair of opposed flat regions at opposite locations within an otherwiseannular body having an interior passageway of generally circular crosssection, improved guidance of the occluder is obtained by providing apair of protrusions or lands 140 which extend from the inner surfaces ofthe annular body 123 and present a pair of oppositely disposed flatsurfaces 141. The protrusions 140 lie substantially to to the right of adiameter of the passageway which is parallel to the pivot axis as viewedin FIG. 14.

Projecting radially inwardly from each of these flat surfaces 141 is apivot post 143 and a pair of stops 145, 147. The pivot posts 143 havearcuate, generally upper and lower surfaces 149a, b which are similarlyformed with the focal point of the radius of curvature lying beyond thecenter point of the pivot post and, if desired, past the oppositesurface of the post, for the purpose described hereinbefore.

The annular body 121 is suitably distended, as described hereinbefore,so as to allow the occluder 125 to be snapped into place with thenotches 139 fitting above the pivot posts 143. As described previously,the length of the pivot post 143 is just less than the depth of thenotches 139 so that the flat edge surfaces 137 of the occluder will bearagainst the flat surface 141 of the protrusions and provide a bearingsurface during pivoting between open and closed positions. In addition,each protrusion 140 is formed with a curved undersurface 150 againstwhich the transitional surface 138 wipes during pivoting action.

In the open position, as shown in FIG. 11 and in broken lines in FIG.14, the occluder is oriented at between about 5° and 15° to thecenterline of the passageway, e.g., at about 10°, lying generallyagainst an inward-facing surface 153 of the stop 145 and with the uppersurface of the notch 139 in contact with the upper surface 149a of thepivot post. There may also be contact between the upstream surface 132of the occluder and the upper stop member 147.

As soon as the pumping stroke of the ventricle ceases for a valve in theaortic position, the back pressure flow lifts the occluder 125 so thatthe lower surface of the notch 139 contacts the arcuate surface 149b ofthe pivot post and the upstream surface 132 contacts a curved surface155 formed on the stop 147 at a location intermediate of the upstreamand downstream surfaces 149a,b of the pivot post 143, both of whichsurfaces 149b guide the pivoting motion. As pivoting movement continuesto an intermediate position, the transitional edge surface 138 of theoccluder essentially wipes along the curved undersurface 150 of theprotrusion. When the occluder 125 reaches the fully closed position (seebroken line illustration "A" in FIG. 14), its major and minor arcuateedges are in contact with the pair of generally semi-elliptical seats161,163 which are formed as a part of the annular body 123 projectinginward from its interior surface. Because each of these seats is shapedwith a generally conical or oblique configuration, the occluder will beself-centering so long as there is clearance at the notches 139, andthere will be line contact between each edge of the occluder and one ofthe seat surfaces, thus providing a more positive seal around theperiphery of the occluder when the heart valve is in the closedposition. This unique self-centering seating feature is applicable toother heart valve designs where a pair of opposed seats can be provided,each of which has a surface that is a portion of generally the surfaceof a frustum of a cone, one being conical upward and the other beingconical downward.

When the ventricle again begins to contract to resume the next pumpingstroke, the pressure against the upstream surface 132 causes pivoting tobegin, and the flow of blood displaces the occluder 125 slightlydownstream so that the upper edge of the notch is in contact with theupper arcuate surface 149a of the pivot post which, along with a curvedupper surface 157 formed on the lower stop 145 (also intermediate of theupstream and downstream surfaces 149a and 149b), defines the path ofpivoting movement from the closed to the open position. An intermediateposition is illustrated in full lines in FIG. 14, and the pivotingmovement is terminated when the undersurface 133 of the occluder comesinto contact with the stop surface 153 in the fully open position, asshown in broken line outline "B" in FIG. 14. In this position, there isexcellent blood flow through the heart valve central passageway because,as best seen in FIG. 11, the post and stop arrangement only extendsminimally into the passageway region and because the additional vacantarea adjacent the surface 150 of the protrusion further decreases theresistance to flow through the valve.

As in the case of the bi-leaflet valve 21, the streamlined configurationprovided by the integral post and stop means, as best seen perhaps inFIG. 10, provides a minimum of disruption to flow through the centralpassageway. Moreover, the integral construction allows one curvedsurface to be blended into the adjacent curved surface thus avoiding thecreation of crevices and/or valleys that tend to permit stagnation andpromote blood clotting.

Depicted in FIGS. 16-23 of the drawings is another alternativeembodiment of a heart valve 221 which includes an annular body 223designed to operate with a pair of flat occluders or leaflets 225.Generally, the same principles of design are executed in the heart valve221 as were hereinbefore explained in detail with respect to thebi-leaflet valve 21, and therefore similar numbers in the 200 series areutilized to refer to comparable components. Moreover, it should beunderstood that, unless specifically stated hereinafter, the functionand construction of the comparable components will be essentially thesame as previously described.

The annular body 223 has an interior surface 227 which defines thepassage or orifice through which the bloodstream will flow and isillustrated with a smooth exterior cylindrical surface 229 for thereason set forth hereinbefore. The interior surface 227 differs slightlyfrom that of the bi-leaflet version shown in FIG. 1 in that the inwardlyextending pivot arrangement is frustoconical instead of cylindrical.

A pair of leaflets 225 are used which are flat and have a uniformthickness throughout. Each leaflet 225 has a straight-edge portion 231,which as best seen in FIG. 17 is oriented at a suitable angle to thedownstream surface 233 of the leaflet so that the two straight-edgeportions 231 abut in substantially face-to-face contact when the pair ofleaflets are in the closed position. Generally, the angle will bebetween about 110° and about 130° C., being of course dependent upon theorientation of the leaflets to the horizontal or transverse plane in theclosed position. In addition, each of the leaflets 225 has a majorarcuate, nearly semicircular, edge 235 (see FIG. 16) and a pair ofintermediate of transitional straight edge portions 237 which are flatand perpendicular to the upstream and downstream surfaces of theleaflets. In addition, each leaflet 225 contains a pair of notches 239disposed in its opposite lateral edges as defined by the straight edgesurfaces 237. As best seen in FIG. 19, the notches are generallytrapezoidal in shape; however, all of the defining edges are rounded asopposed to being sharp.

The passageway-defining interior surface 227 of the annular body 223also has a right circular cylindrical shape for a major portion of itslength but is interrupted by a pair of diametrically opposed flatsections 241 from which the support means for holding and defining themovement of the leaflets 225 radially project. The support meansincludes a pair of pivot posts 243, which are sized to fit within thenotches 239 and which pivot posts are flanked by stop means 245, 247. Ascan be seen from FIGS. 18 and 23, the flanking stop means 245,247project radially farther inward then do the pivot posts 243. Preferably,the pivot posts 243 and the flanking stop means are formed integrallywith one another, and most preferably this overall support structure isformed as an integral part of the annular body 223. This can beaccomplished by machining a pre-shaped body of pyrolytic carbon to finaldimensions; however, it is preferably made using a specially preparedmandrel onto which pyrocarbon is deposited in a form similar to thefinal product. As best seen in FIG. 21, the pivot posts 243 each have apair of opposite arcuate surface portions, a generally upper surface249a and a generally lower surface 249b, which are sometimes referred toas lateral surface portions of the posts 243, so as to be distinguishedfrom the flat end surface 251 of each pivot post, and which arefrustoconical surfaces that are proportioned to interfit with thenotches.

The leaflets 225 are suitably assembled with the annular ring 223 bysuitably distorting the ring, as earlier set forth with respect to theFIG. 1 embodiment. In the assembled heart valve, the depth of the notch239 is slightly greater than the length of the pivot post 243 so thatone of the lateral edge surfaces 237 of each leaflet will bear against afacing flat section 241 of the annular body.

The closed position, depicted in FIG. 17, is substantially the same asin the valve shown in FIGS. 1-8; the arcuate edges 235 of the leaflets225 lie in contact with the interior surface 227 of the annular body.Accordingly, the shape of the arcuate edge 235 will generally be that ofa section of an ellipse, i.e., the intersection between a plane and aright circular cylinder, and the edge is preferably bevelled so as tomore closely seat against the interior cylindrical surface. There may beline contact between the arcuate surface 255 of the stops 247 and theupstream surface 232 of the leaflets, and the straight-edge portions 231of the two leaflets 225 will also abut in substantially face-to-facecontact.

When the pumping stroke occurs, the pressure against the upstreamsurface of the leaflets 225 immediately displaces the leaflets downwardagainst the central stop 245, and pivoting begins guided by the linecontact between the undersurface 233 of the leaflets 225 and the curvedsurfaces 257. In addition, the leaflets will be displaced slightly sothat there is contact between the upper surfaces of the notches 239 andthe arcuate surfaces 249a on the pivot posts.

The integral pivot post and stop arrangement minimizes interference withblood flow, while at the same time providing for effective washing ofthe surfaces to avoid clotting as explained in respect of the heartvalve 21. The movement of the leaflet about the surface 257 as a fulcrumis also primarily a rolling action, with a minimum of sliding movement,which is important to reduce wear. The blending of the integral pivotposts into the stop means allows the design to take advantage of thecontact between the pivot post and the stop means and provides overallstrength without having to precisely match individually machinedcomponents.

Depicted in FIGS. 24-30 of the drawings is another alternativeembodiment of a heart valve 321 which includes an annular body 323designed to operate with a pair of curved occluders or leaflets 325.Generally, the same principles of design are executed in the heart valve321 as were hereinbefore explained in detail with respect to thebi-leaflet valve 21, and therefore similar numbers in the 300 series areutilized to refer to comparable components. Moreover, it should beunderstood that, unless specifically stated hereinafter, the functionand construction of the comparable components will be essentially thesame as previously described.

The annular body 323 has an interior surface 327 which defines thepassage or orifice through which the bloodstream will flow and isillustrated with a smooth exterior cylindrical surface 329 for thereason set forth hereinbefore. The interior surface 327 differs slightlyfrom that of the bi-leaflet version shown in FIG. 1 in that the inwardlyextending pivot arrangement is spherical instead of cylindrical.

A pair of leaflets 325 are used which have a uniform thicknessthroughout but which are curved so as to preferably constitute a sectionof a hollow right circular cylinder, the axis of which is parallel tothe pivot axis of the leaflet. Each leaflet 325 has a straight-edge 331,which as best seen in FIG. 26 is oriented at a suitable angle to thedownstream surface 333 of the leaflet so that the two straight-edges 331abut in substantially face-to-face contact when the pair of leaflets arein the closed position. Generally, the angle will be between about 110°and about 130°, being of course dependent upon the orientation of theleaflets to the horizontal or transverse plane in the closed position.In addition, each of the leaflets 325 has a major arcuate, nearlysemicircular, edge 335 (see FIG. 24) and a pair of intermediate ortransitional straight edge portions 337 which are flat and lie in aplane perpendicular to the straight-edges 331 of the leaflets. Inaddition, each leaflet 325 contains a pair of notches 339 disposed inits opposite lateral edges as defined by the straight edge surfaces 337.As best seen in FIG. 29, the notches are generally spherical in shape,and all of the defining edges are rounded as opposed to being sharp.

The passageway-defining interior surface 327 of the annular body 323also has a right circular cylindrical shape for a major portion of itslength but is interrupted by a pair of diametrically opposed flatsections 341 from which the support means for holding and defining themovement of the leaflets 325 radially project. The support meansincludes two pair of pivot posts 343, which are sized to fit within thenotches 339 and which pivot posts are flanked by stop means 345, 347. Ascan be seen from FIG. 27, the flanking stop means 345,347 projectradially farther inward than do the pivot posts 343. Preferably, thepivot posts 343 and the flanking stop means are formed integrally withone another, and most preferably this overall support structure isformed as an integral part of the entire annular body 323 by depositingpyrolytic carbon upon a suitably shaped mandrel as mentionedhereinbefore. As best seen in FIG. 28, each of the pivot posts 343 hasan arcuate surface which is a section of a sphere. For functionalpurposes, these are referred to as a generally upper surface portion349a and a generally lower surface portion 349b, the post 343 surfaceportions being proportioned to interfit with the notches.

The leaflets 325 are suitably assembled with the annular ring 323 bysuitably distorting the ring, as earlier set forth with respect to theFIG. 1 embodiment. In the assembled heart valve, the depth of the notch339 is slightly greater than the height of the pivot post 343 so thatone of the lateral edge surfaces 337 of each leaflet will bear against afacing flat section 341 of the annular body.

The closed position, depicted in FIG. 26, is substantially the same asin the valve shown in FIGS. 1-8, and the arcuate edges 335 of theleaflets 325 lie in contact with the interior surface 327 of the annularbody. Accordingly, the shape of the arcuate edge 335 will generally bethat of a section of an ellipse, i.e., the intersection between a planeand a right circular cylinder, and the edge is preferably bevelled so asto more closely seat against the interior cylindrical surface. There maybe line contact between the arcuate surface 355 of the stops 347 and theupstream surface 332 of the leaflets, and the straight-edge portions 331of the two leaflets 325 will also abut in substantially face-to-facecontact.

When the pumping stroke occurs, the pressure against the upstreamsurface of each leaflet 325 immediately displaces the leaflets downwardagainst the central stop 345, and pivoting begins guided by the linecontact between the undersurface 333 of the leaflets 325 and the curvedsurfaces 357. In addition, the leaflets will be displaced slightly sothat there is contact between the upper surfaces of the notches 339 andthe arcuate surfaces 349a on the pivot posts.

The integral pivot post and stop arrangement minimizes interference withblood flow, while at the same time providing for effective washing ofthe surfaces to avoid clotting as explained in respect of the heartvalve 21. The movement of the curved leaflet about the surface 357 as afulcrum is primarily a rolling action, with a minimum of slidingmovement, and reduces wear. The curved surface effect of the leaflets inthe open position is felt, as a result of the venturi-like centralpassageway design, to advantageously reduce resistance to blood flow inthis region and may enhance overall performance.

Although the invention has been described with regard to two preferredembodiments, it should be understood that various changes andmodifications as would be obvious to one having the ordinary skill inthis art may be made without departing from the scope of the inventionwhich is defined by the claims appended hereto. For example, withrespect to many of the novel features of the invention, the occluderswhich are shown in various of the embodiments need not be flat but couldbe curved in cross-section, as have been shown in the heart valve designdepicted in FIGS. 24 to 30.

Particular features of the invention are emphasized in the claims thatfollow.

What is claimed is:
 1. A heart valve prosthesis comprisinga generallyannular body which has an interior surface that defines a centralpassageway for blood flow therethrough, occluder means supported on saidbody for alternately blocking and then allowing the flow of bloodthrough said passageway in a predetermined direction, said occludermeans having upstream and downstream major surfaces and being formedwith aligned notch means at opposite locations in the periphery thereof,a pair of aligned pivot posts projecting generally radially inward fromsaid interior surface of said body, which posts have arcuate convexopposite lateral surfaces and are receivable within said notch means,and stop means projecting inward from said interior surface at locationsgenerally flanking each of said pivot posts and extending radiallyfarther inward than said pivot posts, said stop means presenting a pairof curved surfaces in regions adjacent to said pivot posts and overlyingmajor surfaces of said occluder means, each of which curved surfaceslies in a region located intermediate of said opposite arcuate convexside surfaces of said post and extends radially inward thereof so as toprovide a pair of oppositely disposed fulcrums that face each other,flanking said pivot posts, said posts being proportioned to be receivedin said notch means so as to allow at least some nonrotationaldisplacement of said occluder means away from one of said curvedsurfaces toward the other of said curved surfaces whereby supportingcontact is alternated between respective curved surfaces and occludermeans major surfaces as said occluder means repeatedly open and close.2. The prosthesis of claim 1 wherein said stop means is formedintegrally with said pivot posts.
 3. The prosthesis of claim 2 wherensaid stop means curved surfaces are blended into said pivot post arcuatesurface portions.
 4. The prosthesis of claim 3 wherein said stop meansand said pivot posts are integral with said annular body.
 5. Theprosthesis of claim 2 wherein the focal point of each of said convexsurfaces of said pivot posts is located past the center point of saidpivot posts.
 6. The prosthesis of claim 1 wherein said arcuate surfaceportions are cylindrical surface portions.
 7. The prosthesis of claim 1wherein said arcuate surface portions are frustoconical surfaceportions.
 8. The prosthesis of claim 1 wherein said arcuate surfaceportions are spherical surface portions.
 9. The prosthesis of claim 1wherein said occluder means is a single disc having a pair of oppositestraight peripheral segments wherein said notch means are respectivelylocated which are spaced apart a distance less than the diameter of thegenerally circular cross section central passageway.
 10. The prosthesisof claim 9 wherein said pivot post and said stops project from a pair ofprotrusions that lie mainly on one side of a diameter of said passagewayso that said occluder has a major peripheral section that is generallysemicircular and a minor arcuate section that is substantially shorterand that terminates at said pair of opposite straight peripheralsegments, which in turn terminate in a pair of segments perpendicularthereto which are collinear and interconnect with the ends of said majorperipheral section.
 11. The prosthesis of claim 10 wherein each of saidprotrusions includes a generally downstream-facing curved surfaceadjacent which one of said perpendicular segments moves during openingand closing movement of said occluder.
 12. The prosthesis of claim 1wherein said occluder means includes a pair of generally semicircular orsemielliptical discs, each of which has a periphery which includes astraight edge section, a major arcuate edge section, and a pair ofgenerally diametrically opposite straight segments wherein said notchmeans are respectively located.
 13. A heart valve prosthesis comprisingagenerally annular body which has an interior surface that defines acentral passageway for blood flow therethrough, a pair of occluderssupported on said body for alternately blocking and then allowing theflow of blood through said passageway in a predetermined direction, saidoccluders each having upstream and downstream major surfaces and beingformed with aligned notch means at opposite locations in the peripherythereof, two pairs of aligned pivot posts projecting generally radiallyinward from said interior surface of said body, which posts each havearcuate convex upstream and downstream surfaces and are receivablewithin said notch means, and stop means projecting inward from saidinterior surface at locations generally flanking each of said pivotposts and extending radially farther inward than said pivot posts, saidstop means presenting a pair of curved surfaces in regions adjacent tosaid pivot posts and overlying respective major surfaces of saidoccluder means, each of which curved surfaces lies in a region locatedintermediate of said arcuate convex surfaces of said post and extendsradially inward thereof so as to provide a pair of oppositely disposedfulcrums adjacent each pivot post that face each other, flanking saidpivot posts, said posts being proportioned to be received in said notchmeans so as to allow at least some nonrotational displacement of saidoccluder means away from one of said curved surfaces toward the other ofsaid curved surfaces whereby supporting contact is alternated betweenrespective curved surfaces and occluder means major surfaces as saidoccluder means repeatedly open and close.
 14. The prosthesis of claim 13wherein said stop means curved surfaces are blended into said pivot postarcuate surface portions and said stop means and said pivot posts areintegral with said annular body.
 15. The prosthesis of claim 13 whereineach of said occluders is a generally semicircular disc the periphery ofwhich includes a straight edge section, a major arcuate edge section,and a pair of straight segments wherein said notch means arerespectively located, said disc being curved so as to generallyconstitute a section of a hollow right circular cylinder the axis ofwhich is parallel to the pivot axes defined by said aligned pairs ofpivot posts.